awful.tag.move: Fix tag index setting (FS#1249)

Since commit 9c69e857ed, awful.tag.setscreen() unsets a tag's index to make
sure things end up in a sane order on the new screen. Thus, the call to
setscreen() removed the "index" property that tag.move just set.

Fix this by setting the index after the screen.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/awful/tag.lua.in

@@ -56,8 +56,8 @@ function tag.move(new_index, target_tag)
     table.insert(tmp_tags, new_index, target_tag)
 
     for i, tmp_tag in ipairs(tmp_tags) do
-        tag.setproperty(tmp_tag, "index", i)
         tag.setscreen(tmp_tag, scr)
+        tag.setproperty(tmp_tag, "index", i)
     end
 end